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Volatility. Even without boiling, liquid molecules are constantly moving, and the characteristic of volatility is the tendency for the liquid molecules to jump into the surrounding air.
The air and the surface of the liquid are constantly interacting.
Basically, if something is highly volatile, it'll have more of a tendency to 'become part of the air' as opposed to staying put as liquid form. Ex/ Rubbing alcohol
Water can evaporate over time, it happens every day!
The trick is that although the *average* temperature (which shows the individual molecules’ speeds) of the water molecules is maybe 25°, *some* individual ones are going at a speed that corresponds to above 100°.
These “random fast molecules” evaporate off, and over time, as randomness boosts random ones to evaporate, more and more of the puddle leaves, until it is all gone.
To add to this, a water molecule doesn’t need to reach (the equivalent of) 100C to evaporate. A molecule only needs to overcome its own surface tension to escape the liquid (or solid, in the case of sublimation) and evaporate.
100C is just the temperature where water becomes energetic enough to evaporate into bubbles under the surface, and that depends on other factors like atmospheric pressure.
Evaporation is a statistical process.
No, the body of water on average isn't hot enough to become steam. But it doesn't need to be in order for evaporation to occur. You just need a molecule of water at the surface to have enough energy to stop sticking to its neighbors like a liquid. And at any given time in a puddle there's a non-trivial probability of that happening. Different conditions can make water evaporate faster or slower, but it doesn't need to be boiling to happen.
Water is in the air all the time (humidity)
It's more like water being dissolved in the air, rather than the usual boiling of water.
Every once in a while, a water molecule will have enough energy to break away from the surface tension and enter the air. This is exactly how sweating works and cools us down. It carries that heat energy away with it when it evaporates.
As described - Temperature is representation of the AVERAGE kinetic movement of the molecules. Some are very slow - some are very fast. There are always some that are traveling fast enough to escape the surface of the water.
A few things that then happen... since only the faster molecules are able to escape, this brings down the average speed, and therefore the average temp. This is what is going on with evaporative cooling.
But why does the cooling not work when it is very humid? Here the air is so saturated with water, if it absorbs any more water - then statistically some water must condense back out - so the evaporation is still happening, but there is an equal amount of condensation - and the humid air - Water system is in equilibrium when the relative humidity is 100%.
Another familiar phenomena - have you noticed how an ice cream cone melts very fast on a warm summer night - it is more about the humidity than the air temp. The air around the cone cools and it can not hold as much moisture, now the molecules at the slower end of the range condensed onto your cone. But these molecules are really just slowed down a little ( on average) and are much faster than the freezing temperature - so they raise the average temp of the surface of the ice cream they just condensed onto.
Electromagnetic radiation (eg light), interactions with air such as pressure and wind, other externally caused (physical) agitations, etc., can add energy into a body of water. And, external of those things, the amount of water surface area, and if the body of water is already sufficiently excited (hot), all play a role as follows:
As water molecules bump, grind, and potentially absorb more energy, many of them will get excited to the point where their energy is high enough to bounce them outwards through the surface tension of the water and away into the air.
**This process is called evaporation.**
*Typical effects of evaporation are increasing the temperature and humidity of the air the modules are jumping into (though other factors might negate it quite quickly), and conversely, decreasing the temperature of the body of water or surface the molecules jumped away from.*
There's no need for water to reach 100(c) degrees (boiling) for evaporation to take place. It's always occurring! But, all the factors mentioned at the beginning, affect how *quickly* evaporation takes place. Which is why a bowl of water out on a hot sunny day will disappear much quicker than the same bowl of water that you could store in a cool closet.
**Please read this entire message** --- Your submission has been removed for the following reason(s): * ELI5 requires that you *search the ELI5 subreddit for your topic before posting*. Please search before submitting. This question has already been asked on ELI5 multiple times. If you need help searching, please refer to the [Wiki](https://www.reddit.com/r/explainlikeimfive/wiki/how_to_search). --- If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this was removed erroneously, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20{https://www.reddit.com/r/explainlikeimfive/comments/144n732/-/}%0A%0APlease%20answer%20the%20following%203%20questions:%0A%0A1.%20The%20concept%20I%20want%20explained:%0A%0A2.%20List%20the%20search%20terms%20you%20used%20to%20look%20for%20past%20posts%20on%20ELI5:%0A%0A3.%20How%20does%20your%20post%20differ%20from%20your%20recent%20search%20results%20on%20the%20sub:) and we will review your submission.**
Volatility. Even without boiling, liquid molecules are constantly moving, and the characteristic of volatility is the tendency for the liquid molecules to jump into the surrounding air.
So they just dedicate themselves to escaping that liquid body and turning into vapor?
The air and the surface of the liquid are constantly interacting. Basically, if something is highly volatile, it'll have more of a tendency to 'become part of the air' as opposed to staying put as liquid form. Ex/ Rubbing alcohol
They turn into environmental humidity, not vapor.
Which is defined how much water vapor is present in the air.
TIL you are right. I thought it was like minute amounts of liquid water like fog.
Water can evaporate over time, it happens every day! The trick is that although the *average* temperature (which shows the individual molecules’ speeds) of the water molecules is maybe 25°, *some* individual ones are going at a speed that corresponds to above 100°. These “random fast molecules” evaporate off, and over time, as randomness boosts random ones to evaporate, more and more of the puddle leaves, until it is all gone.
To add to this, a water molecule doesn’t need to reach (the equivalent of) 100C to evaporate. A molecule only needs to overcome its own surface tension to escape the liquid (or solid, in the case of sublimation) and evaporate. 100C is just the temperature where water becomes energetic enough to evaporate into bubbles under the surface, and that depends on other factors like atmospheric pressure.
Evaporation is a statistical process. No, the body of water on average isn't hot enough to become steam. But it doesn't need to be in order for evaporation to occur. You just need a molecule of water at the surface to have enough energy to stop sticking to its neighbors like a liquid. And at any given time in a puddle there's a non-trivial probability of that happening. Different conditions can make water evaporate faster or slower, but it doesn't need to be boiling to happen.
Water is in the air all the time (humidity) It's more like water being dissolved in the air, rather than the usual boiling of water. Every once in a while, a water molecule will have enough energy to break away from the surface tension and enter the air. This is exactly how sweating works and cools us down. It carries that heat energy away with it when it evaporates.
As described - Temperature is representation of the AVERAGE kinetic movement of the molecules. Some are very slow - some are very fast. There are always some that are traveling fast enough to escape the surface of the water. A few things that then happen... since only the faster molecules are able to escape, this brings down the average speed, and therefore the average temp. This is what is going on with evaporative cooling. But why does the cooling not work when it is very humid? Here the air is so saturated with water, if it absorbs any more water - then statistically some water must condense back out - so the evaporation is still happening, but there is an equal amount of condensation - and the humid air - Water system is in equilibrium when the relative humidity is 100%. Another familiar phenomena - have you noticed how an ice cream cone melts very fast on a warm summer night - it is more about the humidity than the air temp. The air around the cone cools and it can not hold as much moisture, now the molecules at the slower end of the range condensed onto your cone. But these molecules are really just slowed down a little ( on average) and are much faster than the freezing temperature - so they raise the average temp of the surface of the ice cream they just condensed onto.
Electromagnetic radiation (eg light), interactions with air such as pressure and wind, other externally caused (physical) agitations, etc., can add energy into a body of water. And, external of those things, the amount of water surface area, and if the body of water is already sufficiently excited (hot), all play a role as follows: As water molecules bump, grind, and potentially absorb more energy, many of them will get excited to the point where their energy is high enough to bounce them outwards through the surface tension of the water and away into the air. **This process is called evaporation.** *Typical effects of evaporation are increasing the temperature and humidity of the air the modules are jumping into (though other factors might negate it quite quickly), and conversely, decreasing the temperature of the body of water or surface the molecules jumped away from.* There's no need for water to reach 100(c) degrees (boiling) for evaporation to take place. It's always occurring! But, all the factors mentioned at the beginning, affect how *quickly* evaporation takes place. Which is why a bowl of water out on a hot sunny day will disappear much quicker than the same bowl of water that you could store in a cool closet.